1. Macromolecules and the Origin of Life

2. 3.1 What Kinds of Molecules Characterize Living Things?
Molecules in living organisms: proteins, carbohydrates, lipids, nucleic acids
Most are polymers of smaller molecules called monomers.
Macromolecules: polymers with molecular weights >1000

3. Table 3.1

4. 3.5 What Are the Chemical Structures and Functions of Nucleic Acids?
Nucleic acids: DNA—(deoxyribonucleic acid) and RNA—(ribonucleic acid)
Polymers—the monomeric units are nucleotides.
Nucleotides consist of a pentose sugar, a phosphate group, and a nitrogen- containing base.

5. Figure 3.23 Nucleotides Have Three Components

6. 3.5 What Are the Chemical Structures and Functions of Nucleic Acids?
DNA—deoxyribose
RNA—ribose

7. 3.5 What Are the Chemical Structures and Functions of Nucleic Acids?
The “backbone” of DNA and RNA consists of the sugars and phosphate groups, bonded by phosphodiester linkages.
The phosphate groups link carbon 3′ in one sugar to carbon 5′ in another sugar.
The two strands of DNA run in opposite directions.

8. Figure 3.24 Distinguishing Characteristics of DNA and RNA (Part 1)

9. Figure 3.24 Distinguishing Characteristics of DNA and RNA (Part 2)

10. 3.5 What Are the Chemical Structures and Functions of Nucleic Acids?
DNA bases: adenine (A), cytosine (C), guanine (G), and thymine (T)
Complementary base pairing:
A—T
C—G
Purines pair with pyrimidines by hydrogen bonding.

11. 3.5 What Are the Chemical Structures and Functions of Nucleic Acids?
Instead of thymine, RNA uses the base uracil (U).
RNA is single-stranded, but complementary base pairing occurs in the structure of some types of RNA.

12. Figure 3.25 Hydrogen Bonding in RNA

13. Table 3.3

14. 3.5 What Are the Chemical Structures and Functions of Nucleic Acids?
DNA is an informational molecule: information is encoded in the sequences of bases.
RNA uses the information to determine the sequence of amino acids in proteins.

15. 3.5 What Are the Chemical Structures and Functions of Nucleic Acids?
The two strands of a DNA molecule form a double helix.
All DNA molecules have the same structure—variation is in the sequence of base pairs.

16. Figure 3.26 The Double Helix of DNA

17. 3.5 What Are the Chemical Structures and Functions of Nucleic Acids?
DNA carries hereditary information between generations.
Determining the sequence of bases helps reveal evolutionary relationships.
The closest living relative of humans is the chimpanzee.

18. 3.5 What Are the Chemical Structures and Functions of Nucleic Acids?
Other roles for nucleotides:
ATP—energy transducer in biochemical reactions
GTP—energy source in protein synthesis
cAMP—essential to the action of hormones and transmission of information in the nervous system